California's "Basic Speed Law" says you must:

Question

The "Basic Speed Law" states that you may never drive faster than is safe for current conditions. For example, if you drive at 45 mph in a 55 mph zone during a dense fog, even though you are below the posted limit, you may be cited for driving "too fast for conditions."

Accepted Answer

Never drive faster than is safe for current conditions.

Answer

Keep your speed close to that of other traffic.

Answer

Always drive at the posted speed limit.